1. Field of the Invention
The present invention relates to an image shake correcting device for correcting image shake caused by movement of the hands, for example, in an optical apparatus such as a camera.
2. Description of the Related Art
Hitherto, various devices have been proposed for the purpose of correcting shake of optical systems such as a camera, i.e., restricting vibrations caused by movement of the hands to stabilize an image. In a typical one of shake correcting devices for use in cameras, a part or the whole of a photographing optical system is driven in accordance with camera shake information detected by a shake sensor so that image shake on the focus plane is restricted. Such an image shake correcting device is disclosed in, for example, Japanese Patent Laid-Open No. 9-43658.
In a conventional image shake correcting device, however, it is generally known that, for satisfactorily restricting vibrations caused by movement of the hands or vibrations having a similar frequency distribution, the shake sensor, the correcting optical system, and response frequency bands of the shake sensor and the driving systems are selected and set in accordance with the target vibrations. The following disadvantages therefore occur when a conventional image shake correcting device is mounted on a tripod or the like, for use with a camera.
1) Even in the case where shake correction is not required, the shake correcting mechanism continues operation and hence power consumption is increased.
2) In a still camera, a high-frequency impact occurs, though a small amplitude of displacement, due to a mirror quickly returned at the time of release or a shutter mechanism (about 20-50 Hz for shake due to the mirror operation and about 100-200 Hz for shake due to the shutter operation), and may cause an error output of the shake sensor. In such a case, the shake correcting mechanism operates to perform shake correction unrelated to shake of the camera body, and thereby promotes image shake rather than corrects image shake.
3) Even in the case where no shake is generated, the shake correcting mechanism operates in response to a low-frequency drift signal (jitter) outputted from vibration detecting means, and performs shake correction unrelated to shake of the camera body, thus promoting image shake rather than correcting image shake.
To overcome the above disadvantages, it has been already proposed to inhibit the image shake correcting operation or to modify a characteristic of the image shake correction control upon detection of the fact that the image shake correcting device is mounted on a support member such as a tripod. The former proposal is disclosed in, e.g., Japanese Patent Laid-Open No. 4-56831, and the latter proposal is disclosed in, e.g., Japanese Patent Laid-Open No. 4-328534.
These proposals, however, have problems as follows. In the proposal disclosed in Japanese Patent Laid-Open No. 4-56831, when it is detected that an image shake correcting device is mounted on a support member such as a tripod, the image shake correcting operation is totally inhibited. Accordingly, shake of a high-frequency and small amplitude (referred to as xe2x80x9ccamera shakexe2x80x9d hereinafter) cannot be corrected, which occurs due to the reaction upon the mirror""s quick return or the shutter operation at the time of release in a camera.
Also, Japanese Patent Laid-Open No. 4-328534 intends to overcome the problem of Japanese Patent Laid-Open No. 4-56831. When it is detected that an image shake correcting device is mounted on a support member such as a tripod, the image shake correcting operation is not inhibited and a characteristic of the image shake correction control is modified. However, a characteristic of the image shake correction control is modified according to a single pattern. Optimum shake correction is not always achieved with a single pattern modification of the control, taking into account the shutter speed of a camera at photo-shooting. At a low shutter speed, for example, primarily a low-frequency drift signal (jitter) of the shake sensor becomes not negligible and a photographed image deteriorates.
One aspect of the present invention resides in an image shake correcting device applied to an apparatus (such as a camera) in which image shake is to be corrected. The device comprises an image shake correcting unit for correcting image shake in accordance with an output of a shake detecting unit for detecting a shake condition; a support condition determining unit for determining whether the apparatus, in which image shake is to be corrected, is supported in a predetermined stationary condition; a shutter speed information determining unit for determining a shutter speed at photo-shooting; and a varying unit for varying a response manner of the image shake correcting means to the output of the shake detecting means in accordance with a combination of the determination made by the support condition determining means and the determination made by the shutter speed information determining means.
With the above features, the image shake correcting device is operated in an optimum mode suitable for various use situations, such as whether the apparatus (camera) is handheld or fixedly supported on a tripod or the like.